a. Field of the Invention
This disclosure relates to a system for performing one or more diagnostic and/or therapeutic medical procedures, the system comprising, in part, a magnetic field-based medical positioning system. More particularly, this disclosure relates to various components of the system for performing one or more diagnostic and/or therapeutic medical procedures, wherein the components are configured for use in a magnetic field environment created by the magnetic field-based medical positioning system.
b. Background Art
A number of different types of medical positioning systems may be used to aid in the performance of various medical diagnostic and therapeutic procedures relating to different parts of the human anatomy, such as, for example, the heart. Among other things, and generally speaking, these systems may provide the ability to determine the position and orientation (P&O) of one or more medical devices disposed within the body of the patient, such as, for example, catheters and sheaths, for visualization and navigation purposes.
One such type of medical positioning system is a magnetic field-based medical positioning system. Magnetic field-based systems generally include one or more magnetic field generators attached to or placed near the patient bed or another component in the operating environment. The field generators are configured to provide controlled, low-strength AC magnetic fields in an area of interest (i.e., an anatomical region) that are used to determine and track the P&O of one or more magnetic sensors disposed in or on a medical device disposed within the area of interest. More particularly, each magnetic sensor, which may comprise a magnetic coil, is configured to detect and generate a respective signal indicative of one or more characteristics of the magnetic field(s). The medical positioning system then processes the generated signals to produce one or more P&O readings associated with the sensors (and thus the medical device). The P&O of the medical device can thereafter be tracked relative to the magnetic field(s).
As briefly described above, medical devices that may be used with such medical positioning systems include elongate medical devices such as catheters and sheaths. These medical devices generally comprise an elongate shaft having a proximal end portion, a distal end portion, and one or more sensors mounted in or on the shaft at or near the distal end portion thereof. As also briefly described above, the sensors of the medical device may comprise magnetic sensors in the form of coils that are configured to allow the system to determine the P&O of the sensor, and therefore by extension, the medical device. More particularly, each sensor may comprise a loop of wire wound a predetermined number of times around a small diameter core to form a coil having a size that is suitable for packaging within the shaft of the medical device, and for generating a current when placed in a magnetic field that is used by the system to determine the P&O of the sensor.
One drawback to the use of these types of medical devices in conjunction with a magnetic field-based medical positioning system is that any loops of wire that are considered separate or apart from the sensor can act as a magnetic pickup when subjected to magnetic fields. This may result in noise or interference being added to the signal generated by the sensor, thereby potentially adversely impacting the accuracy of the P&O determination based thereon (i.e., causing an error in the P&O of the sensor determined based on the signal generated by the sensor). For example, a wire that is wrapped numerous times around a core to form a coil may have two ends or leads extending from the coil. These leads are routed from the coil down the shaft of the medical device where they are terminated in an electrical connector that allows for the sensor to be electrically coupled to other components of, for example, the medical positioning system or components that are intermediate thereto (e.g., amplifiers, processors, etc.). However, when arranged within the shaft of the medical device, these two leads may serve to form a loop of wire that may generate a current when subjected or exposed to a magnetic field. As described above, this may result in the addition of noise or interference to the current signal being transmitted from the sensor.
One conventional technique used to address the above-described problem is to arrange the two leads in a twisted pair pattern along the lengths of the leads from the sensor to the termination point. Such an arrangement is known to prevent, or at least substantially minimize, magnetic pickup in the wires. Accordingly, by preventing magnetic pickup along the length of the shaft of the medical device, interference or noise that may adversely impact the signals generated and transmitted by the sensor is prevented or at least substantially minimized. However, while this technique has been useful in limiting interference generated along the length of the shaft of the medical device, it does not completely solve the problem with respect to other areas or locations of the medical device or within the system of which it is a part.
More particularly, as described above, the two leads of the sensor are terminated at an electrical connector that may be disposed at or near the proximal end portion of the shaft (e.g., within or near the handle of the device located proximate the proximal end portion of the shaft). To do so, the two leads are typically untwisted in order to be coupled (e.g., soldered, crimped, etc.) to respective pins of the electrical connector. However, the length of the pins, the relatively large distance therebetween, and the length of the untwisted portion of the leads proximate the connector combine to form a loop comprised of the pins of the connector and the untwisted portions of the leads. Because the handle portion of the medical device, and therefore, the electrical connector to which the leads are coupled, is disposed in close proximity to the patient during a procedure, the electrical connector may be subjected or exposed to the magnetic field(s) applied by the medical positioning system. As a result, the loop formed by the untwisted portion of the leads and the pins of the electrical connector can act as a magnetic pickup, and therefore, a current may be induced in the loop by the magnetic field(s). As described above, such a generated current may result in noise or interference to the signal generated and transmitted by the sensor, which may introduce not in significant error in the sensor location determined therefrom.
The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.